_WCRTLINK short _WCI86FAR _CGRAPH _arc( short x1, short y1, short x2, short y2,
/*====================*/ short x3, short y3, short x4, short y4 )
/* This function draws an elliptical arc. The virtual ellipse is defined by
the rectangle whose opposite corners are ( x1, y1 ) and ( x2, y2 ). The
intersections of the vectors from the center of the ellipse to the points
( x3, y3 ) and ( x4, y4 ) define the start and end points respectively
where the arc is drawn in a counter clockwise direction. */
{
short success;
if( _GrProlog() ) {
success = _L2arc( _VtoPhysX( x1 ), _VtoPhysY( y1 ),
_VtoPhysX( x2 ), _VtoPhysY( y2 ),
_VtoPhysX( x3 ), _VtoPhysY( y3 ),
_VtoPhysX( x4 ), _VtoPhysY( y4 ) );
if( success ) {
_moveto( _GetLogX( _ArcInfo.end.xcoord ),
_GetLogY( _ArcInfo.end.ycoord ) );
}
_GrEpilog();
} else {
success = 0;
}
return( success );
}
_WCRTLINK short _WCI86FAR _CGRAPH _getarcinfo( struct xycoord _WCI86FAR *start,
/*===========================*/ struct xycoord _WCI86FAR *end,
struct xycoord _WCI86FAR *fillpoint )
/* This function returns the starting and ending points of the last arc
or pie drawn. The points are in viewport coordinates. The fillpoint
is an inside point that can be used by floodfill to fill a pie slice.
This is not used in WATCOM C Graphics which uses a specialized fill
routine for pie slices. */
{
short success;
short x1, y1;
short x2, y2;
short x3, y3;
long xprod;
success = ( _ErrorStatus == _GROK );
if( success ) {
start->xcoord = _GetLogX( _ArcInfo.start.xcoord );
start->ycoord = _GetLogY( _ArcInfo.start.ycoord );
end->xcoord = _GetLogX( _ArcInfo.end.xcoord );
end->ycoord = _GetLogY( _ArcInfo.end.ycoord );
x1 = _ArcInfo.start.xcoord - _ArcInfo.centre.xcoord;
y1 = _ArcInfo.start.ycoord - _ArcInfo.centre.ycoord;
x2 = _ArcInfo.end.xcoord - _ArcInfo.centre.xcoord;
y2 = _ArcInfo.end.ycoord - _ArcInfo.centre.ycoord;
x3 = 3 * ( x1 + x2 ) / 8;
y3 = 3 * ( y1 + y2 ) / 8;
xprod = (long) x1 * y2 - (long) x2 * y1;
if( xprod == 0 ) {
if( x1 != x2 || y1 != y2 ) { // 180 degrees apart
x3 = sgn( y1 ); // offset from centre
y3 = -sgn( x1 );
}
} else if( xprod > 0 ) { // more than 180
x3 = -x3;
y3 = -y3;
}
fillpoint->xcoord = _GetLogX( x3 + _ArcInfo.centre.xcoord );
fillpoint->ycoord = _GetLogY( y3 + _ArcInfo.centre.ycoord );
}
return( success );
}
_WCRTLINK struct xycoord _WCI86FAR _CGRAPH _getviewcoord_w( double x, double y )
/*===============================================================
Map (x,y) from window coordinates to viewport coordinates. */
{
struct xycoord pt;
if( _GraphMode() ) {
pt.xcoord = _GetLogX( _WtoPhysX( x ) );
pt.ycoord = _GetLogY( _WtoPhysY( y ) );
} else {
pt.xcoord = 0;
pt.ycoord = 0;
}
return( pt );
}
